Recently, with the rapid development of wireless communication technology, the fourth generation (4G) network technology (up-link rate of 20 megabits per second (Mbit/s) and down-link rate of 100 Mbit/s) is basically able to meet the needs of a variety of mobile communications services. However, with the rapid development of mobile Internet technology and Internet of things technology, it almost subverts the traditional mobile communication business models. These emerging mobile communication services have provided new demands for the development of mobile communication networks, such as high traffic density, mass connections and ultra-low latency, which have led to the research and development of fifth generation (5G) communication technology. At present, the standardization of 5G mobile communication technology is gradually completed, and the equipment using 5G technology will also be gradually commercial around 2020. The data services of Giga-bit level in 5G will give users a totally new experience.
Through using the millimeter (mm) wave antenna, the problem of narrow bandwidth is solved. Through using the antenna array and beamforming technologies, the problem of attenuation of free space in millimeter wave band is solved. However, the problem of radiation direction in the 5G antenna is still existed. A typical radiation pattern of a 4G antenna which is an omnidirectional antenna. The radiation pattern is approximately circular in the horizontal direction, so it can achieve a full signal coverage of free space in horizontal direction with appropriate gain. A typical radiation pattern of a 5G antenna which is a directional antenna. The signal can only be transmitted and received in specified direction range pointed by terminal antenna. Even if the beam scanning is realized by phase shifter, it can only extend the signal radiation range in the lateral direction of radiation pattern of antenna array, and other directions remain blind spots of signal radiation, therefore it is difficult to achieve omnidirectional radiation characteristic of 4G antennas.